1. Field of the Invention
The present invention relates to a socket for electrical parts for detachably accommodating and holding an electrical part such as a semiconductor device (called as “IC package” hereinlater), and more particularly, the present invention relates to a socket for electrical parts that prevents a solder ball as a terminal of electrical parts from sticking to contact portions of contact pins.
2. Related Art of the Invention
As a conventional “socket for electrical parts” of this kind, there is provided an IC socket for detachably accommodating an IC package as an “electrical part”.
The IC package includes, for example, a BGA (Ball Grid Array) type of IC package in which solder balls as a number of terminals are provided to the lower surface of the package body so as to protrude downward in a grid (lattice) arrangement.
The IC socket is provided with a contact pin having a pair of elastic pieces (paired elastic pieces), on each tip portion of which a contact portion is formed to contact and separate from a side surface portion of the solder ball of the IC package. And one of the elastic pieces is designed to be elastically deformed by being pushed with a movable plate that can slide laterally (transversely).
With making the movable plate slide, one of the paired elastic pieces of the contact pin is elastically deformed so as to widen the distance between a pair of contact portions (paired contact portions). Next, the solder ball is inserted into the widened space between the paired contact portions. Then the movable plate moves back to its original position, so that the contact portion of the one of the elastic pieces goes back toward its original position, thereby the solder ball is clamped by the paired contact portions to electrically connect the solder ball and the contact pin.
In this state described above, such performance test as a burn-in test is carried out. After the testing, the movable plate is slid, as described above, to displace the contact portion of the one of the elastic pieces so as to widen the distance between both contact portions of the contact pin. The paired contact portions are to be separated from the solder ball. Then the IC package is drawn off from the IC socket using, for example, an automated machine.
According to the above-mentioned structure, the IC package is designed to be able to be inserted in and drawn off from the IC socket, without applying extra force, by only sliding the movable plate, aiming to improve the operation efficiency significantly.
However, in such conventional IC packages as mentioned above, the solder balls often stick to some contact portions of the contact pins, because the solder balls are softened by the heat applied to the IC package of up to about 125° C. during the burn-in test. Under these conditions, the solder ball often remains stuck to one of the paired contact portions and do not separate from the contact portion even when the distance of both contact portions are widened by displacing the contact portion of one of the elastic pieces. In these situations, it is often the case that the IC package can not be drawn off from the IC socket without applying extra force on the IC package.